Field of the Invention
The present invention relates to a magnetic recording medium which is preferably used in a magnetic recording and reproducing apparatus such as a hard disk drive, and a magnetic recording and reproducing apparatus including the magnetic recording medium.
Priority is claimed on Japanese Patent Application No. 2015-136832, filed on Jul. 8, 2015 and Japanese Patent Application No. 2016-038320, filed on Feb. 29, 2016, the content of which is incorporated herein by reference.
Description of Related Art
In order to improve recording density of a magnetic recording and reproducing apparatus, a magnetic recording medium suitable for high recording density has been developed.
Examples of the magnetic recording medium include a magnetic recording medium in which a magnetic layer recording information, a protective layer formed of carbon or the like, and a lubricant layer are formed on a substrate for a magnetic recording medium in this order.
The protective layer protects the information recorded on the magnetic layer and increases slidability of a magnetic head with respect to the magnetic recording medium. However, it is not possible to obtain sufficient durability of the magnetic recording medium only by disposing the protective layer on the magnetic layer.
For this reason, in general, the lubricant layer is formed by applying a lubricant onto the surface of the protective layer, and thus, the durability of the magnetic recording medium is improved. By disposing a lubricant layer, it is possible to prevent the magnetic head of the magnetic recording and reproducing apparatus from being directly in contact with the protective layer. In addition, by disposing the lubricant layer, a frictional force between the magnetic recording medium and the magnetic head sliding on the magnetic recording medium is significantly reduced. In addition, the lubricant layer has a function of preventing the magnetic layer or the like of the magnetic recording medium from being corroded due to impurities entering from the surrounding environment.
In the related art, examples of the lubricant used in the lubricant layer of the magnetic recording medium include a perfluoropolyether-based lubricant, an aliphatic hydrocarbon-based lubricant, and the like.
For example, in Patent Document 1, a magnetic recording medium is disclosed in which a lubricant of perfluoroalkyl polyether having a structure of HOCH2—CF2O—(C2F4O)p-(CF2O)q-CH2OH (p and q are integers.) is applied onto a carbon protective film.
In Patent Document 2, a magnetic recording medium is disclosed onto which a lubricant formed of perfluoroalkyl polyether (tetraol) denoted by HOCH2CH(OH)—CH2OCH2CF2O—(C2F4O)p-(CF2O)q-CF2CH2OCH2—CH(OH)CH2OH (p and q are an integer.) is applied.
In Patent Document 3, a magnetic recording medium including a lubricant layer in which a phosphazene compound and a compound having perfluorooxy alkylene unit are mixed in a specific range is disclosed. In addition, in Patent Document 3, it is disclosed that the lubricant layer has a high bonding force with respect to the protective layer, and even in a case where the layer thickness of the protective layer decreases, a high coating ratio can be obtained.
In Patent Document 4, a lubricant containing a compound denoted by R1—C6H4O—CH2CH(OH)CH2OCH2—R2—CH2—O—R3 is disclosed.